1. Field of the Invention
The present invention relates to an inkjet recording method, and more particularly to an inkjet recording method capable of recording in a circular shape and simultaneously recording on areas with different resolutions by use of a line-array inkjet head.
2. Description of the Related Art
Printing a label for displaying a content of record, a title, etc. on the surface of a disk-shaped information recording medium (which will hereinafter be simply called a disk) such as a CD (compact disk) or a DVD (digital versatile disk) has hitherto involved creating a printing plate based on a design for printing and performing the printing within a series of manufacturing processes. In this case, a method of printing the label for display on the surface of the disk is classified into a method of printing the label directly on the surface of the disk and a method of temporarily printing the label on a seal different from the disk and pasting this label-printed seal onto the surface of the disk.
Further, the printing method has involved utilizing mainly screen printing, offset printing, thermal recording (melt thermal transfer and sublimation thermal transfer) or an electrophotography, or the like.
Further, with advancements of the technologies and a spread of the personal computers over the recent years, a multiplicity of disks in which information can be written, such as a CD-R and a CD-RW come to be utilized. Namely, those disks are utilized for publishing software components on a small scale or for a personal use such as writing the information by a PC user by himself or herself for the reasons of being inexpensive, easy to handle and large in recording capacity.
The mass-print oriented screen printing and offset printing described above are not suited to high-mix low-volume printing applications in which a content of the label to be printed differs for each group including a few sheets or every single sheet as in the case of the label printing for the CD-R, or the like.
Moreover, the thermal recording described above might cause transformation of the disk due to a decline of image quality and the heat applied when printed. The electrophotography likewise has problems both in the image quality and in the heat when fixed, and is therefore unpreferable to the label printing of the disk.
By contrast, the inkjet recording method is a method of jetting ink particles onto a recording target medium. The inkjet recording method has no problem about the transformation of the disk explained above because there occurs no contact with the recording medium when printing, and thus, the costs for printing are made lower with the much higher image quality.
JP5-238005 A discloses a technology of printing the label on the disk by use of the inkjet method described above.
This technology is that the disk is rotated at a predetermined rotational frequency and an inkjet device disposed facing a label printing surface of the rotating disk is used to print print data such as print target characters and pictures on the label printing surface of the disk, so that the labels with their designs different for every single sheet can be printed.
In the case of rotating the disk and printing by the inkjet head disposed facing the rotating surface of the disk, however, there arises a problem in that a peripheral speed differs between an inner peripheral side and an outer peripheral side of the rotating disk, and hence there occurs a difference in dot density of the ink recorded (transferred) between the inner peripheral side and the outer peripheral side if ejecting the ink with a fixed ink dot size at a fixed ink ejection frequency, resulting in unevenness in image density and a decline of image quality.
Accordingly, upon recording in the circular shape on the rotating disk by use of the inkjet recording method, it is required that the ink ejection frequency or the dot size of the ink ejected be so controlled as to be changed in accordance with the peripheral speed of the disk. The technology disclosed in JP 5-238005 A does not particularly include such a control scheme, with the result that the unevenness in image density might occur.